The invention relates to an apparatus for controlling braking liquid pressure which may be used in a braking system of a vehicle to produce a proportionate reduction in an input liquid pressure to derive an output liquid pressure.
An apparatus for controlling braking liquid pressure is used in order to produce braking efforts of an equal magnitude for both the front and the rear wheels during the initial phase of a braking operation when such efforts are at their low level, and to reduce the braking effort applied to the rear wheels as compared to that applied to the front wheels so that both the front and the rear wheels may be locked simultaneously whenever the braking effort exceeds a given value. At this end, such apparatus includes a plunger which is responsive to the pressure prevailing in a master cylinder to open or close a valve, which in turn produces a proportionate reduction in the pressure transmitted from the master cylinder before it is applied to a rear wheel cylinder.
In a usual apparatus for controlling braking liquid pressure, a plunger used therein has opposite end faces of different areas which are subject to respective pressures so as to be operated in accordance with the master cylinder pressure which is applied to the both end faces. Accordingly, the plunger is slidably disposed within a bore formed in a body. The bore has portions of an increased and a reduced diameter, and the portion of the increased diameter is closed by a plug in order to contain the plunger within the bore. Thus, a combination of the body which contains the plunger and the plug is used. However, the combination of the body and the plug presents a limit in reducing the size of the profile of the apparatus and also poses a problem in that a high accuracy is required in assembly and machining to achieve the concentricity between the body and the plug since the plunger is disposed in sliding contact with both the body and the plug. It is proposed to crimp the plug to the body so as to provide an integral construction. With this construction, a torque of an increased magnitude is applied to the crimped regions when mounting the apparatus on the master cylinder, and also an excessive load is applied to the crimped regions during the operation, thus presenting another difficulty that an increased strength requirement is imposed upon the crimped regions.